Method for conversion of materials including asbestos

ABSTRACT

A method for conversion of a material including asbestos includes: crumbling a fibrous structure of the material such that the material is crumbled into smaller particles; transporting the crumbled material into a microwave reactor and mixing with an agent facilitating heating of the material; heating the crumbled material by beams of focused polarized electromagnetic radiation in a microwave band and maintaining the smaller particles at a temperature for a period of time for structural transformation; removing the heated crumbled material from the microwave reactor and cooling the material; and subjecting the cooled crumbled material to a process of final crumbling.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.12/115,333 filed on May 5, 2008, now U.S. Pat. No. 8,197,768 which is acontinuation of International Application No. PCT/PL2006/000075 filed onNov. 2, 2006, which claims the benefit of P 377957, filed Nov. 3, 2005.The disclosures of the above applications are incorporated herein byreference.

FIELD

The present invention concerns a method for conversion of materialsincluding asbestos as well as an apparatus for conversion of materialsincluding asbestos designed, first of all, for rendering harmlessdismantled building elements, in particular cement-asbestos plates.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

The known method for rendering harmless fibrous building materials, likeasbestos, which comprises heating it till it reaches the temperature ofabout 1400° C., close to its melting temperature, by contacting it withfumes of a traditional furnace. As a result, asbestos fiber meltdown andfading of its crystal structure takes place and asbestos is transformedinto a safe non-fibrous structure.

An example of the traditional method can be found in the internationalpatent application published as WO 91/00123. It discloses a process forthe mineralogical conversion of waste asbestos to a non-asbestosproduct. The waste asbestos is treated with a mineralizing agent andthen heated for a period of time sufficient to convert the asbestos tothe non-asbestos product. The mineralizing agent is preferably awater-soluble alkali metal borate or alkali metal silicate.

The process of heating is carried out in a conventional oven until thematerial achieves a temperature above 2000° F. Due to isolationproperties of some materials containing asbestos, there is needed a longtime of heating such materials. For this reason, energy outlay toeffectively utilize (making harmless) asbestos is very large.Introduction of additional substances in WO 91/00123 has as its aim toboost the asbestos fibres destruction as the result of thermochemicalprocesses. The publication presents only laboratory examples whichillustrates the difficulties to adapt the disclosed process tocommercial applications in the industrial scale.

A German patent specification DE 19526495 A discloses another method anda device designed for thermal modification of building materials, mainlyasbestos, binded during creation of hydrates. This method comprisestreating fibrous materials with microwave radiation inside a processingchamber, with wave length ranging from 10-1 m to 10-6 m, whereas atleast a part of the radiation fits into a range of maximum absorption,as a result the materials are heated so much that their fibrousstructure disintegrates.

The processed material is introduced inside the chamber in portions andheated up to the desired temperature in a certain time dependant onradiation power. A device for realizing such a method has a processingchamber to which a microwave generator is attached having at least oneradiator emitting microwave radiation. The processing chamber has aloading inlet and an unloading outlet which are close by sealing gates,and the whole device has a special shield preventing the microwaveenergy spreading. Placing radiators opposite to each other, as well asrotating the processed material, is very advantageous. At least oneradiation beam penetrates into the processing chamber of the device, thesaid beam emitted by parabolic antennas and directed crosswise to thechamber axis. Another embodiment of such a device comprises a containerwith a processing zone, across which the processed material is moved. Amicrowave generator with a radiator is connected to the container, saidradiator creating microwave radiation in the processing area. Processingchamber has an inlet and an outlet through which processing material isbeing inserted and taken out. Both inlet and outlet are closed by airlocks and the whole device has a protective shield.

Because materials containing asbestos poorly absorb microwave radiation,maximum absorption during their processing can be reached only within anarrow range of microwave length and frequency. Effective heating ofmaterials, merged as a result of the creation of hydrates, is achievedby the use of radiation in the band of so called polar moleculechemically bounded resonant absorption. It corresponds to a frequency ofover 4 GHz, and infrared radiation. In industrial practice it ispermitted to use microwave generators with frequencies 2.45 GHz and 915MHz, which correspond to wave length 12, 24 centimeters and 32,77centimeters accordingly. Of course, in case of need one can usegenerators with other, optimally selected, frequencies and respectivelybigger power; however they are very expensive and almost inaccessible.Moreover, the temperature of about 1400° C., which is necessary todisintegrate the fibrous structure of asbestos, with known methods ofits thermal processing, requires huge amounts of energy. Additionally,radiators in the form of parabolic antennas, used with generators of theknown device, can be used only for emitting the non-polarized microwavefield. Placing radiators opposite to each other brings only partialsuccess, because the maximum field intensity has a local range. Due tothis fact we can obtain an effective heating only in a small area of theconverted material. A significant disadvantage of non-polarizedradiation is a risk of harmful coupling between generators havingradiators situated opposite to each other. This effect of generatorcoupling can become even more serious when the emitted electromagneticwaves reach a frequency at which there is weak field absorption by theprocessed material.

In practice, the method acc. to DE 19526495 A cannot be used, as onecannot use the microwave generators for frequencies different thanapproved for industries, i.e. 2450 MHz and 915 MHz, among others.Further, high power generators for frequencies above 3 GHz are difficultto obtain and very expensive—they are used only in scientific research.

The European Patent Application EP 1 588 783 teaches a process forinactivating industrial waste including crystalline or semi-crystallinematerial containing H₂O or crystal water, which consists in subjectingthe industrial wastes to high power microwaves to explosive like convertthe H₂O or crystal water into the vapor phase and to destroy its solidstate structure.

It teaches also an apparatus having generally a chamber with input,output and conveying means, and a microwave source. It does not discloseany specific method as such nor a definite construction of an apparatus,so it is not suitable for the direct industrial application. It istaught there that the material should not be crumbled and its subjectmatter consists on strong local overheating (“hot spot”). Strong localoverheatings cause uneven heating of the material. As the result, somepart are having lower temperature and they do not react sufficiently(some areas with fibrous asbestos structure may remain).

It is equally important, that by the methods acc. to DE 19526495 A andEP 1 588 783 it is not possible to make harmless the asbestos containedin asbestos cloth, asbestos ropes or different asbestos boards, as suchwaste do not contain water or watery silicon compounds.

SUMMARY

In one form, a method for conversion of materials including asbestosconsists in heating the materials and transforming a fibrous crystallinestructure of asbestos into non-fibrous structure under anelectromagnetic field. The method includes crumbling the fibrousstructure such that the material is crumbled into smaller particles;transporting the crumbled material into a microwave reactor and mixingwith an agent facilitating heating of the material; heating the crumbledmaterial by beams of focused polarized electromagnetic radiation in amicrowave band and maintaining the smaller particles at a temperaturefor a period of time for structural transformation; removing the heatedcrumbled material from the microwave reactor and cooling the material;and subjecting the cooled crumbled material to a process of finalcrumbling.

In another form, a method for conversion of materials including asbestosincludes: crumbling the materials into material particles; mixing thematerial particles with a first agent; and heating the materialparticles by beams of electromagnetic radiation.

In still another form, a method for conversion of materials includingasbestos comprising heating them and transforming the fibrouscrystalline structure of asbestos into non-fibrous structure underinfluence of electromagnetic field is disclosed. The method according tothe disclosure is characterized by the fact that converted material iscrumbled and then the crumbled material is transported into a microwavereactor. Material particles, while being crumbled and/or transported,are mixed with an agent facilitating their heating, and after theirintroduction into the reactor material particles are heated up totemperature of their structural transformation by way of many polarizedbeams of focused electromagnetic radiation in microwave band, withfrequency from about 300 MHz to about 3,000 MHz. Then the product of thethermal processing is removed from the reactor, cooled, and is subjectedto the process of final crumbling.

In other features, converted material is crumbled into particles withdimensions not exceeding about 5 mm. Material particles while beingcrumbled are mixed with sodium tetra boron water solution or with sodiumhydroxide, whereas during the transportation phase chunks of materialsare being mixed with sodium silicate water solution or with potassiumsilicate water solution. The most beneficial effect is obtained whenmaterial particles are mixed with an agent facilitating their heating involume proportion from about 3:1 to about 1:1. In order to transformfibrous, crystal asbestos structure into a non-fibrous one, materialparticles mixed with an agent facilitating their heating are heated upto temperature from about 900° C. to about 1,100° C. and kept in suchtemperature for a period of time lasting from about 2 to about 15minutes.

An apparatus for conversion of materials including asbestos equippedwith a thermal reactor including a heating chamber having at least onemicrowave generator, according to the disclosure, is characterized bythe fact that it comprises a crusher for converted material, a conveyorfor particles of the crumbled material, a feeder/dispenser of the agentfacilitating heating and a thermal microwave reactor, whereas the feederis connected to the crusher and/or to the conveyor, and the reactorheating chamber, made of microwave radiation non-absorbing material, islocated at an outlet of the conveyor and placed in a metal housing,whereas a microwave generator unit with microwave radiators is fixed tothe metal housing.

In a beneficial solution of the disclosure, the feeder is attached tothe crusher or simultaneously to the crusher and to the conveyor. Inanother beneficial solution, the feeder is attached only to theconveyor. The heating chamber and the housing of the reactor have bothforms of stationary vertical cylinders situated coaxially, between whichan insulating space is created, and microwave generators are placed on acircumference of the housing, the said microwave generators havingradiators emitting polarized waves, whereas radiators located oppositeto each other emit polarized waves with mutually perpendicularpolarization.

The radiators in one form have advantageously the form of flattenedtubes. It is preferred if the crusher, provided for the process of finalcrumbling of the product of the thermal processing, is locatedunderneath the heating chamber of reactor. In the another form, theheating chamber and the reactor housing both have horizontally shaped,coaxially situated, cylinders between which an insulating space iscreated, whereas the heating chamber is mounted on rotary bearings inthe housing and connected to the driving source, and microwavegenerators are located in series along the housing and have radiatorsemitting polarized waves.

Although the materials that include asbestos have low heat conductivity,thanks to their crushing and mixing with a supporting agent, theircapacity for the absorption of microwave radiation is significantlyincreased. Also materials free from hydrates obtain this beneficialfeature. Under the influence of focused action of many polarized beamsof radiation, one receives a fast and uniform heating of material in allits volume. The additional effect of using an agent facilitating theheating allows for lowering of the temperature, at which thetransformation of fibrous, crystalline structure of asbestos into aharmless structure without fibers takes place. As a result, the processof a microwave heat treatment requires relatively small quantities ofelectric energy. Apart from the kind of absorption and the compositionof the utilized material the device may be equipped, according to thedisclosure, by microwave generators with a working frequency of about2.45 GHz or about 915 MHz.

Thanks to flat tube radiators, which produce polarized beams ofradiation, it is possible to avoid harmful coupling between generatorsand also obtain a relatively large concentration of microwave energy.

Further areas of applicability will become apparent from the descriptionprovided herein. It should be understood that the description andspecific examples are intended for purposes of illustration only and arenot intended to limit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

In order that the invention may be well understood, there will now bedescribed forms thereof, given by way of example, reference being madeto the accompanying drawings, in which:

FIG. 1 is a side view of a device for heating and destruction of theasbestos fibres, constructed in accordance with the principles of thepresent disclosure, owing to the crumbling of the material to therequired size, soaking it with chosen additives and as a result of itsheating by focused and polarised microwaves, takes place quickly andindependently of the composition of waste containing asbestos;

FIG. 2 is a side view of a device for effectively using availablemicrowave generators emitting microwaves with approved (for theindustrial applications) frequencies of about 2,450 MHz and about 915MHz constructed in accordance with the principles of the presentdisclosure; and

FIG. 3 is a side view of a device for reducing the energy outlay fordestruction of the asbestos fibres constructed in accordance with theprinciples of the present disclosure.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application, or uses.

The subject of the disclosure in the form of an apparatus for conversionof materials including asbestos is presented in an exemplary form in adrawing in which FIG. 1 presents a simplified representation of avertical section of the device, having a microwave reactor with astationary, vertical heating chamber. FIG. 2 presents a perspective viewof the reactor from FIG. 1, and FIG. 3 presents a simplifiedrepresentation of the device, having reactor with a rotary, horizontalheating chamber.

The apparatus according to the disclosure presented in the FIGS. 1 and 2is basically composed of a hammer crusher 1, a screw conveyor 2, afeeder 3 and a thermal microwave reactor 4, which constitute the workinginstallation.

A loading inlet 5 and a body 6 of the crusher 1 are sealingly closed,which prevents released asbestos fibers from getting through to theenvironment. The feeder 3 is attached to the conveyor 2 and supplies itwith the agent that facilitates heating particles of the crushedmaterial. As needed, the feeder 3 is attached simultaneously to both thecrusher 1 and conveyor 2 or is attached only to the crusher 1. Theconveyor 2 also has also a function of a mixer for producing a uniformmixture of particles of the crushed material and the agent thatfacilitates its heating. The body of the conveyor 2 is connected by adust filter 7 with an exhaust fan 8. The chamber 9 is mounted in a metalhousing 10, which protects the environment against the influence ofunwanted microwave radiation. A set of four microwave generators 11,equipped with four microwave radiators 12, is fixed to the housing 10.The chamber 9 and the housing 10 both have a form of stationary,basically pipe like, cylinders 13 and 14, which are placed verticallyand situated coaxially to each other. Between the cylinders 13, 14 thereis created a vertical, annular insulation space 15, which—depending onthe need—is filled with air or with a layer of the thermal insulationmaterial, which is not shown in the drawing. The microwave generators 11are uniformly displaced along the circumference of the housing 10 andtheir radiators 12 have a form of tubes 16 with flattened outlets. Whena flattened outlet of one horn 16 is directed horizontally then theflattened outlet of the opposite horn 16 is directed vertically. Theradiators 12_situated opposite to each other emit polarized waves withmutually perpendicular polarizations. Under the heating chamber 9 thereis a disk crusher 17, which serves as a crusher of the product of heattreatment, the said product having a form that is similar to pumice. Thehorizontal disk of the crusher 17 constitutes the closing of the chamberoutlet 9. The body of the crusher 17 has a connection to an air or watercooling system that is not presented, and is equipped with containers 18for collecting the crushed final product. Another form of the apparatusaccording to the disclosure is presented on the FIG. 3. It alsocomprises the crusher 1 with the loading inlet 5 a screw conveyor 2, afeeder 3 and a thermal microwave reactor 4 a, whereas the filter 7 andthe fan 8 are attached to the conveyor 2. The heat resistant, ceramicheating chamber 9 a and a metal housing 10 a of the reactor 4 a bothhave the form of basically pipe like cylinders 13 a and 14 a, which areplaced horizontally and situated coaxially to one another. Between thecylinders 13 a and 14 a there is a horizontal, annular insulation space15 a that is filled by air. The heating chamber 9 a, in the form of arotary drum, is mounted in a stationary housing 10 a and connected tothe drive 19, whereas the outlet of the conveyor 2 is introduced insidethe chamber 9 a. In the end part of the housing 10 a of the reactor 4 athere is a rotary fan crusher 17 a, whereas at the outlet of the housingthere are placed the containers 18 a for the crushed final product. Themicrowave generators 11 are placed in series along the lower part of thehousing 10 a and have the radiators 12 in form of tubes 16 a withflattened outlets. The radiators 12 emit polarized waves with mutuallyperpendicular polarizations.

During the work of the apparatus shown in the FIG. 1 and FIG. 2,elements containing asbestos are placed in the crusher 1 inlet 5. Forexample, cement-asbestos plates, asbestos-gypsum plates, asbestosblankets and asbestos cords, which are crushed into small particles ofdiameters not exceeding 5 millimeters. During conversion ofcement-asbestos plates, called popularly asbestic tiles, all the crushedmaterial is mixed, already in the crusher 1, with sodium tetra boronwater solution or with constant sodium hydroxide, brought from thefeeder 3, in proportions of about 2:1 or about 1:1. Wet particles fallinto the screw conveyor 2, in which they are further mixed with sodiumsilicate water solution or with potassium silicate water solution,brought from the feeder 3, in proportion 2:1. This two step process hasits justification, because the sodium tetra boron and sodium hydroxidereduce the surface tension and make the further soaking of the materialwith sodium silicate water solution or with potassium silicate watersolution easier. When asbestos blankets or cords are conversed, it isenough to mix their crushed particles only during the transport phase inthe screw conveyor 2, with sodium silicate water solution or withpotassium silicate water solution in proportions of about 3:1. In caseof conversion of asbestos-gypsum plates, the crushed material is mixedinside the crusher 1 with sodium hydroxide and with sodium silicatewater solution brought from the feeder 3 in proportions of about 2:1.Next, wet particles of material are introduced into the reactor 4 bymeans of conveyor 2. After filling reactor 4 heating chamber 9 withproperly wetted material, the heating process begins at temperaturesfrom about 900° C. up to about 1,100° C. The heating of the materialtakes place following the action of many polarized beams of stronglyconcentrated electromagnetic radiation, in microwave frequency band ofabout 2.45 GHz or about 915 MHz, created by generators 11 and emittedinto the chamber 9 by means of the tube radiators 12. To achieve thefull conversion of the fibrous, crystal structure of asbestos into astructure deprived of fibers, particles of cement-asbestos plates arekept in that temperature for about 15 minutes, particles ofasbestos-gypsum plates for about 10 minutes, whereas blanket particlesand cord particles for about 2 or 3 minutes. As a result of materialmeltdown its structure takes the form similar to that of pumicestone,whereas the content of the chamber 9 decreases its original volume and,under the influence of gravity, gradually moves downwards. After theworking cycle of the reactor 4 is finished, a disc crusher 17 isactivated and it crushes the product of thermal processing andsimultaneously cools it down passing it into the containers 18 in theend. With the properly selected capacity of the crusher 1 and the rightflow capacity of the conveyor 2, the reactor 4 can work continuously. Inthe device shown in the FIG. 3, the process of conversion of asbestosmaterials can similarly proceed in a cyclic order or continuously. Afterfilling the heating chamber 9 a of the reactor 4 a with wet material, acyclic process comprising heating the heating chamber 9 a content toworking temperature, by microwave generators 11 with tube radiators 12takes place. Moreover the heating chamber 9 a is put into a rotarymotion, causing the gradual displacement of the heated material movesfrom the chamber inlet to its outlet. After the assigned time, theheating process ends and thermally modified material is removed outsidethe chamber 9 a. In the outlet part of the reactor 4 a housing 10 a, thematerial is crushed and cooled down with the help of fan crusher 17 a,and then it is passed to the suitably placed containers 18 a. Continuousfunctioning of this device can be obtained by appropriate adjustment ofthe capacity of the crusher 1, the flow capacity of the conveyor 2 andthe rotary speed of the heating chamber 9 a.

It should be noted that the disclosure is not limited to the embodimentdescribed and illustrated as examples. A large variety of modificationshave been described and more are part of the knowledge of the personskilled in the art. These and further modifications as well as anyreplacement by technical equivalents may be added to the description andfigures, without leaving the scope of the protection of the disclosureand of the present patent.

What is claimed is:
 1. A method for conversion of a material includingasbestos consisting in heating the material and transforming a fibrouscrystalline structure of asbestos into non-fibrous structure under anelectromagnetic field, the method comprising: crumbling the fibrousstructure such that the material is crumbled into smaller particles;transporting the crumbled material into a microwave reactor and mixingwith an agent facilitating heating of the material; heating the crumbledmaterial by beams of focused polarized electromagnetic radiation in amicrowave band and maintaining the smaller particles at a temperaturefor a period of time for structural transformation; removing the heatedcrumbled material from the microwave reactor and cooling the material;and subjecting the cooled crumbled material to a process of finalcrumbling.
 2. The method according to claim 1 further comprising mixingthe material particles with a sodium tetra boron water solution whilethe material particles are being crumbled.
 3. The method according toclaim 1 further comprising mixing the material particles with sodiumhydroxide while the material particles are being crumbled.
 4. The methodaccording to claim 1 further comprising mixing the material particleswith a sodium silicate water solution while being transported.
 5. Themethod according to claim 1 further comprising mixing the materialparticles with a water potassium silicate solution while beingtransported.
 6. The method according to claim 1, wherein the mixing ofthe agent in the final crumbling is such that the material particles areheated in a volume proportion from about 3:1 to about 1:1.
 7. The methodaccording to claim 1, wherein the smaller particles are cement-asbestosand are maintained at a temperature from about 900° C. to about 1,100°C. for about 15 minutes.
 8. The method according to claim 1, wherein thesmaller particles are asbestos-gypsum and are maintained at atemperature from about 900° C. to about 1,100° C. for about 10 minutes.9. The method according to claim 1, wherein the smaller particles arecomprised of blankets and cords and are maintained at a temperature fromabout 900° C. to about 1,100° C. for about 2 to about 3 minutes.
 10. Amethod for conversion of materials including asbestos, the methodcomprising: crumbling the materials into material particles; mixing thematerial particles with a first agent; and heating the materialparticles by beams of electromagnetic radiation.
 11. The methodaccording to claim 10, wherein heating the material particles by beamsof electromagnetic radiation comprises heating the material particles byfocused and polarized microwaves.
 12. The method according to claim 10,wherein the first agent facilitates the heating and is selected from agroup consisting of a sodium tetra boron water solution and sodiumhydroxide.
 13. The method according to claim 10, further comprisingmixing the material particles with a second agent after the mixing thematerial particles with the first agent.
 14. The method according toclaim 13, wherein the second agent facilitates the heating and isselected from a group consisting of a sodium silicate water solution anda potassium silicate water solution.
 15. The method according to claim13, further comprising transporting the material particles to a thermalreactor while the material particles are mixed with the second agent.16. The method according to claim 15, further comprising maintaining thematerial particles at a temperature of 900° C. to 1100° C. for 10 to 15minutes during the heating.
 17. The method according to claim 10,further comprising cooling the material particles after the heating. 18.The method according to claim 17, further comprising crumbling thematerial particles into smaller particles after the cooling.
 19. Themethod according to claim 10, further comprising rotating the materialparticles during the heating.
 20. The method according to claim 10,further comprising emitting polarized beams of concentratedelectromagnetic radiation in microwave frequency band in the range of915 MHZ to 2.45 GHZ by means of tube radiators.